Adjustable-Rate vs. Fixed-Rate Mortgages in San Diego: How Each One Works
A fixed-rate mortgage keeps the same interest rate for the whole loan, while an adjustable-rate mortgage, or ARM, has a rate that is set for an introductory period and then changes at regular intervals. The Consumer Financial Protection Bureau says an ARM's rate is based on an index plus a set margin, and rate caps limit how far it can move.
The short answer
- A fixed rate stays the same for the life of the loan. An ARM changes after its introductory period.
- Three caps limit an ARM: the first adjustment, each later adjustment and the lifetime total.
- Common cap values are 2% or 5% at the first adjustment, 1% or 2% after that and 5% for the lifetime, according to the CFPB.
- You can ask your lender to calculate the highest payment you could ever owe.
How the two loans differ
| Fixed-rate | Adjustable-rate (ARM) | |
|---|---|---|
| Interest rate | Same for the whole loan | Fixed for an introductory period, then adjusts |
| Principal and interest payment | Stays the same | Can rise or fall after the introductory period |
| Starting rate | Often higher | Often lower at the start |
| Main risk | Locking in a rate that later falls | Payment rising after the rate adjusts |
The CFPB explains that an ARM's rate is tied to an index plus a margin, may be subject to caps and can change at regular intervals after an introductory period. It recommends checking how high the rate and payment can go before taking one.
How rate caps work
The CFPB describes three caps:
- Initial adjustment cap: limits the first change after the fixed period. Common values are 2% or 5%, measured from the starting rate.
- Subsequent adjustment cap: limits each later change, measured from the previous rate. Common values are 1% or 2%.
- Lifetime adjustment cap: limits the total change over the loan, measured from the starting rate. The most common value is 5%.
Some loans also have a floor that limits how low the rate can drop. The CFPB says to compare caps when comparing ARMs, because two lenders can offer the same starting rate with different caps. The caps appear on your Loan Estimate or Truth-in-Lending disclosure.
A payment example
At the time this article was written, I checked that the national average 30-year fixed rate was 7.40% as of October 15, 2026. The national survey I follow does not publish ARM rates, so the ARM rate below is made up to show how the math works. Say you borrow $800,000. The ARM starts at 6.40% for five years, then follows the CFPB's common caps of 2 points at the first adjustment, 1 point at each later one and 5 points for the lifetime. This is for illustration only.
| Loan and period | Rate | Principal and interest |
|---|---|---|
| Fixed rate, all 30 years | 7.40% | $5,539 |
| ARM, first 5 years | 6.40% | $5,004 |
| ARM, after the first adjustment (up 2 points) | 8.40% | $5,973 |
| ARM, after the next adjustment (up 1 more point) | 9.40% | $6,472 |
| ARM, at the lifetime cap (up 5 points in total) | 11.40% | $7,549 |
In this example the ARM payment is about $535 lower each month during the first five years. After the first adjustment it would be about $434 higher than the fixed payment, and at the lifetime cap it would be about $2,010 higher. These figures assume the rate rises the full amount each time, which is the worst case the caps allow. Rates could also stay flat or fall.
Who might consider each
- A fixed rate fits buyers who want a payment that never changes and plan to stay a long time.
- An ARM may fit buyers who expect to sell or refinance before the introductory period ends, and who could still afford the capped payment if they could not.
Refinancing is never guaranteed, because it depends on your credit, income, home value and rates at that time. Ask a lender to calculate the highest payment you could ever owe, and compare that to your budget. If you want to lower a fixed payment instead, read my guide to rate buydowns and discount points.
Questions to ask your lender
- How long is the introductory period, and when is the first adjustment?
- What index and margin does the loan use?
- What are the initial, subsequent and lifetime caps?
- What is the highest payment I could owe?
- Is there a prepayment penalty?
My list of questions to ask a mortgage lender covers more. For timing, see buying now or waiting for rates to drop.
What this guide cannot promise
I cannot predict where rates will go. Loan terms, caps and starting rates differ by lender, and the example above is a teaching tool. Your Loan Estimate shows the real terms.
My advice for San Diego buyers
- Ask for fixed and adjustable quotes on the same loan amount.
- Compare the caps, not only the starting rate.
- Ask for the highest payment you could ever owe.
- Only choose an ARM if you could afford the capped payment.
- Read the adjustment terms on your Loan Estimate before you lock.
A note on advice
I am a REALTOR®, not a lender, attorney, tax professional or financial advisor, so this guide is general information. Your lender can tell you what you qualify for, and a CPA or attorney can answer tax and legal questions.
Call or text me at (619) 402-4614 or send me a message.
Call or text (619) 402-4614Contact Trevor LandressRelated guides
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- Final Walkthrough Checklist for San Diego Home Buyers
- How Much Income Do You Need to Buy a Home in San Diego?
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Frequently asked questions
What is an adjustable-rate mortgage?
It is a loan whose rate is set for an introductory period and then changes at regular intervals. The rate is based on an index plus a set margin and may be subject to caps.
What are ARM rate caps?
They limit how much the rate can change. The CFPB describes an initial adjustment cap, a subsequent adjustment cap and a lifetime cap.
What are common cap values?
According to the CFPB, common values are 2% or 5% for the initial cap, 1% or 2% for later adjustments and 5% for the lifetime.
Where do I find the caps on my loan?
They appear on your Loan Estimate or Truth-in-Lending disclosure.
Can I find out the highest payment I could owe?
Yes. The CFPB suggests asking your lender to calculate the highest payment you could ever owe.
About the author
Trevor Landress is a San Diego REALTOR® with Coldwell Banker West (DRE# 02126901). He was born and raised in San Diego and has been licensed since 2021.
Trevor helps homeowners sell, guides first-time buyers through the home buying process and assists investors with their next acquisition. His work includes negotiating offers, analyzing market trends, building pricing strategies and running marketing campaigns for his listings.
He serves clients across San Diego County, from coastal communities like La Jolla, Del Mar and Carlsbad to neighborhoods inland.
Trevor is part of the Campbell Group, a three-generation real estate team, and he and the Campbell Group consistently rank as a top producing team at Coldwell Banker West each month. He writes these guides to help San Diego buyers and sellers navigate an ever-changing market. To talk through your plans, call or text (619) 402-4614 or contact Trevor Landress.
How I help San Diego home buyers
I help buyers sort out their budget, understand their loan options with a lender, search for homes, write and negotiate offers, keep track of inspection and contingency deadlines and stay organized through closing.
How I help San Diego home sellers
I help sellers price their home, prepare it for the market, market it to buyers, review and negotiate offers and manage the steps from an accepted offer to closing.
Market data note: figures are pulled and tracked by Trevor Landress from public records and market reports and are accurate as of the month stated.
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